Crystal structure and microwave dielectric properties of alpha-(Ca1-xSrx) SiO3 (x=1 and 0.8) ring silicates for millimeter-wave applications

摘要

Millimeter-wave wireless communications in a high-level information society have been expanding in terms of high-density data transfer and radar for pre-crash safety systems. alpha-wollastonite (CaSiO3) based and SrSiO3 based solid solutions (s.s.) in the CaSiO3-SrSiO3 eutectic binary system are expected as millimeter-wave dielectrics because of low dielectric constant as described in a previous paper. In this paper, crystal structures of SrSiO3 and Ca0.2Sr0.8SiO3 compounds are analyzed by Rietveld method using X-ray powder diffraction (XRPD) patterns obtained at the PF-KEK, Tsukuba, Japan. Covalencies of Si-O bonds are calculated through the bond strength obtained by the bond length, which at x = 0.8 were higher than that of at x = 1 as (Ca1-xSrx)SiO3. The lowest dielectric constant (epsilon(r)) and highest Qf value at x = 0.8 with epsilon(r)=6.62, Qf= 66,700 GHz and tau(f)=-40 ppm/degrees C were explained by the covalencies. (C) 2016 Elsevier Ltd. All rights reserved.